<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 300px;
            height: 300px;
            margin: 200px 200px;
            background-color: palegreen;
        }
    </style>
</head>
<body>
    <div class="box"></div>

    <script>
        var box = document.querySelector('.box');

        box.addEventListener('mousemove', function(e) {
            var x = e.pageX - this.offsetLeft;
            var y = e.pageY - this.offsetTop;
            this.innerHTML = 'x坐标是' + x + ' y坐标是' + y;
        })

    </script>
</body>
</html>